U.S. patent application number 12/734164 was filed with the patent office on 2010-09-30 for hybrid automatic repeat request method of a downlink tunnel.
This patent application is currently assigned to ZTE Corporation. Invention is credited to Yang Liu, Hongyun Qu.
Application Number | 20100246478 12/734164 |
Document ID | / |
Family ID | 40625358 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100246478 |
Kind Code |
A1 |
Liu; Yang ; et al. |
September 30, 2010 |
HYBRID AUTOMATIC REPEAT REQUEST METHOD OF A DOWNLINK TUNNEL
Abstract
A hybrid automatic repeat request method of a downlink tunnel
comprising the following steps: the base station transmits the
tunnel data comprising the protocol data unit of multiple mobile
stations to the access relay station via the tunnel link, and
receives the feedback from the relay station until the access relay
station receives the data correctly; the access relay station
analyzes the protocol data unit of each mobile station from the
tunnel data, transmits the protocol data unit of each mobile
station to the corresponding mobile station, and performs the
corresponding process after receiving the feedback from each mobile
station.
Inventors: |
Liu; Yang; (Shenzhen,
CN) ; Qu; Hongyun; (Shenzhen, CN) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
ZTE Corporation
Shenzhen
CN
|
Family ID: |
40625358 |
Appl. No.: |
12/734164 |
Filed: |
November 20, 2007 |
PCT Filed: |
November 20, 2007 |
PCT NO: |
PCT/CN2007/003287 |
371 Date: |
April 15, 2010 |
Current U.S.
Class: |
370/315 |
Current CPC
Class: |
H04L 1/1812 20130101;
H04L 2001/0097 20130101; H04L 1/1887 20130101 |
Class at
Publication: |
370/315 |
International
Class: |
H04B 7/14 20060101
H04B007/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2007 |
CN |
200710165178.1 |
Claims
1. A hybrid automatic repeat request method of a downlink tunnel,
comprising the following steps: a base station transmitting tunnel
data that comprise protocol data units of multiple mobile stations
to an access relay station via a tunnel link; the access relay
station determining its own reception of the tunnel data that
comprise protocol data units of multiple mobile stations, and
transmitting feedback to the base station via the tunnel link, or
receiving feedback from each of the mobile stations about reception
of a corresponding protocol data unit which is sent via an access
link, and according to the feedback from each of the mobile
stations, applying for bandwidth for retransmission or
concentratedly transmitting the feedback from each of the mobile
stations to the base station via the tunnel link, wherein the
access relay station extracting the protocol data unit of each of
the mobile stations after successfully receiving the tunnel data
that comprise protocol data units of multiple mobile stations, and
transmitting the protocol data unit of each of the mobile stations
to each of the mobile stations via the access link, the tunnel link
being made up of multi-hop relay stations, the relay station
accessing the base station being the 1.sup.st hop relay station,
and the relay station accessing the mobile station being the
n.sup.th hop relay station, wherein, the 1.sup.st hop, the 2.sup.nd
hop, . . . , the (n-1).sup.th hop relay station not transmitting
feedback immediately to the base station after receiving the tunnel
data.
2. The method according to claim 1, wherein, the base station
allocates corresponding channels for data transmission and feedback
to each of the hop relay stations before transmitting the tunnel
data.
3. The method according to claim 2, wherein, each of the hop relay
stations knows the feedback channel allocated to it by the base
station via its own calculation.
4. The method according to claim 3, wherein, when the t.sup.th hop
relay station on the tunnel link fails to receive the tunnel data
that comprise protocol data units of multiple mobile stations, the
t.sup.th hop relay station transmits repeat request information to
the base station via the (t-1).sup.th hop, the (t-2).sup.th hop, .
. . , the 1.sup.st hop relay station on the feedback channel which
is allocated to it by the base station.
5. The method according to claim 4, wherein, if the t.sup.th relay
station receives the tunnel data that comprise protocol data units
of multiple mobile stations in the i.sup.th frame, then the
t.sup.th relay station transmits feedback from a downlink relay
station to the base station in the (I+m).sup.th frame, wherein,
m=M*q+(M+1)*k, M is the number of hops between the t.sup.th hop
relay station and the access relay station, q is the number of
fixed delay frames of each of the hop relay stations for the tunnel
data that comprise protocol data units of multiple mobile stations,
k is a delay for hybrid automatic repeat request feedback for the
tunnel data that comprise protocol data units of multiple mobile
stations on each of the hop relay stations.
6. The method according to claim 4, wherein, the t.sup.th relay
station encodes the repeat request information, and transmits
encoded repeat request information to the base station via the
feedback channel which is allocated to it by the base station.
7. The method according to claim 5, wherein, if the access relay
station receives the tunnel data that comprise protocol data units
of multiple mobile stations successfully, then the access relay
station transmits reception acknowledgement information to the base
station immediately, otherwise encodes the repeat request
information immediately, and transmits the encoded repeat request
information to the base station.
8. The method according to claim 7, wherein, if the tunnel data
that comprise protocol data units of multiple mobile stations is a
tunnel burst, then the t.sup.th hop relay station determines
whether it receives the protocol data unit of each of the mobile
stations successfully according to a cyclic redundancy check code
which is carried by the protocol data unit of each of the mobile
stations itself.
9. The method according to claim 8, wherein, the encoded repeat
request information includes information with respect to the
t.sup.th hop relay station and information with respect to
connections of which the protocol data units are not received
successfully by the t.sup.th hop relay station.
10. The method according to claim 9, wherein, the access relay
station retransmits the corresponding protocol data unit to the
mobile station which fails to receive the corresponding protocol
data unit via pre-scheduled air interface resource.
11. The method according to claim 10, wherein, when the
pre-scheduled air interface resource is insufficient for
retransmitting the corresponding protocol data unit to the mobile
station which fails to receive the corresponding protocol data
unit, the access relay station applies again to the base station
for the air interface resource for retransmission.
12. The method according to claim 11, wherein, the access relay
station transmits the feedback from the multiple mobile stations
concentratedly to the base station via the tunnel link or a
dedicated hybrid automatic repeat response link.
13. The method according to claim 7, wherein, if the tunnel data
that comprise protocol data units of multiple mobile stations is a
tunnel packet, then the t.sup.th hop relay station determines
whether it receives the tunnel data that comprise protocol data
units of multiple mobile stations successfully according to a
cyclic redundancy check code of the tunnel data that comprise
protocol data units of multiple mobile stations.
14. The method according to claim 13, wherein, the encoded repeat
request information includes information with respect to the
t.sup.th hop relay station.
15. The method according to claim 14, wherein, the access relay
station retransmits the corresponding protocol data unit to the
mobile station which fails to receive the corresponding protocol
data unit via pre-scheduled air interface resource.
16. The method according to claim 15, wherein, when the
pre-scheduled air interface resource is insufficient for
retransmitting the corresponding protocol data unit to the mobile
station which fails to receive the corresponding protocol data
unit, the access relay station applies again to the base station
for the air interface resource for retransmission.
17. The method according to claim 16, wherein, the access relay
station transmits the feedback from the multiple mobile stations to
the base station via the tunnel link or a special hybrid automatic
repeat response link.
18. The method according to claim 6, wherein, if the access relay
station receives the tunnel data that comprise protocol data units
of multiple mobile stations successfully, then the access relay
station transmits reception acknowledgement information to the base
station immediately, otherwise encodes the repeat request
information immediately, and transmits the encoded repeat request
information to the base station.
19. The method according to claim 18, wherein, if the tunnel data
that comprise protocol data units of multiple mobile stations is a
tunnel burst, then the tth hop relay station determines whether it
receives the protocol data unit of each of the mobile stations
successfully according to a cyclic redundancy check code which is
carried by the protocol data unit of each of the mobile stations
itself.
20. The method according to claim 19, wherein, the encoded repeat
request information includes information with respect to the
t.sup.th hop relay station and information with respect to
connections of which the protocol data units are not received
successfully by the t.sup.th hop relay station.
21. The method according to claim 20, wherein, the access relay
station retransmits the corresponding protocol data unit to the
mobile station which fails to receive the corresponding protocol
data unit via pre-scheduled air interface resource.
22. The method according to claim 21, wherein, when the
pre-scheduled air interface resource is insufficient for
retransmitting the corresponding protocol data unit to the mobile
station which fails to receive the corresponding protocol data
unit, the access relay station applies again to the base station
for the air interface resource for retransmission.
23. The method according to claim 22, wherein, the access relay
station transmits the feedback from the multiple mobile stations
concentratedly to the base station via the tunnel link or a
dedicated hybrid automatic repeat response link.
24. The method according to claim 18, wherein, if the tunnel data
that comprise protocol data units of multiple mobile stations is a
tunnel packet, then the t.sup.th hop relay station determines
whether it receives the tunnel data that comprise protocol data
units of multiple mobile stations successfully according to a
cyclic redundancy check code of the tunnel data that comprise
protocol data units of multiple mobile stations.
25. The method according to claim 24, wherein, the encoded repeat
request information includes information with respect to the
t.sup.th hop relay station.
26. The method according to claim 25, wherein, the access relay
station retransmits the corresponding protocol data unit to the
mobile station which fails to receive the corresponding protocol
data unit via pre-scheduled air interface resource.
27. The method according to claim 26, wherein, when the
pre-scheduled air interface resource is insufficient for
retransmitting the corresponding protocol data unit to the mobile
station which fails to receive the corresponding protocol data
unit, the access relay station applies again to the base station
for the air interface resource for retransmission.
28. The method according to claim 27, wherein, the access relay
station transmits the feedback from the multiple mobile stations to
the base station via the tunnel link or a special hybrid automatic
repeat response link.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to the field of
communications, and relates more specifically to a hybrid automatic
repeat request method of a downlink tunnel in a multi-hop relay
system.
BACKGROUND
[0002] In order to enlarge the coverage of communication systems
and to increase capacity of systems, one or more relay stations
(Relay Station, shortened as RS) may be set between a multi-hop
relay base station (Multi-hop Relay Base Station, shortened as
MR-BS) and mobile stations (Mobile Stations, shortened as MS).
Channel resource allocation must be implemented by an MR-BS in a
centralized relay system, therefore the design of a hybrid
automatic repeat request (Hybrid Automatic Repeat Request,
shortened as HARQ) of the relay system that schedules a RS in a
centralized manner is relatively complex.
[0003] The form of an HARQ will be increased accordingly due to the
introduction of an RS, and the typical forms are an end-to-end HARQ
and a hop-by-hop HARQ. With regard to the end-to-end HARQ of the
centralized relay, an uplink control station has allocated a
corresponding feedback channel for each RS to transfer an ACK/NACK
before the RS transmits a certain HARQ burst (also called
sub-burst). In existing technologies, the RS knows the feedback
channel allocated to itself by calculation after receiving the
burst which is to be transferred, and then transmits feedback over
corresponding resource. Once the burst fails to be transferred by
the relay, a delay for retransmission may also become large due to
the long feedback time because air interface resource must be
allocated by the MR-BS when centralized scheduling is adopted.
[0004] Moreover, as shown in FIG. 1, when one RS applies access to
multiple MSs, one relay tunnel can be set up between the access RS
and the MR-BS. Protocol data units (shortened as PDUs) of multiple
MSs can make up one tunnel burst by the MR-BS to act as a basic
unit of the HARQ to be transmitted in one frame. After the tunnel
burst reaches the access RS successfully, the RS restores the PDUs
of each MS, and continues to accomplish the HARQ on the access
link.
[0005] Presently, in the IEEE802.16j standard draft, the tunnel
data can be divided into two modes: a tunnel packet mode and a
tunnel burst mode. In the tunnel packet mode, the PDU of each MS is
assembled as one tunnel packet to be transmitted. The tunnel packet
has its own packet header (including a Tunnel Connection Identifier
(Tunnel CID, shortened as TCID)) and a Cyclic Redundancy Check
(Cyclic Redundancy Check, shortened as CRC) code. One burst may
have tunnel packets on different tunnels. In the tunnel burst mode,
the TCID is provided in a downlink map information element (DL MAP
IE), therefore the tunnel data may be taken as one burst of a
physical layer. One burst can only include PDUs of MSs on the same
tunnel. A reduced connection identifier (RCID) of each PDU is
replaced by the same TCID.
[0006] However, an HARQ method completely involving tunnel data
transmission is never prescribed in existing technologies. For
example, an ACK of each MS cannot be transferred on a tunnel
individually when a tunnel packet or a tunnel burst is used for
transmission. The advantage of tunnel transmission may be lost if a
TCID is not added to tunnel data while a data burst of each MS is
fed back individually, because at this moment, it may seem that
multiple MSs perform the HARQ independently.
SUMMARY
[0007] Whereas the above-mentioned one or more problems, the
present invention provides a hybrid automatic repeat request method
of a downlink.
[0008] According to embodiments of the present invention, the
hybrid automatic repeat request method of a downlink comprises the
following steps: a base station transmits tunnel data comprising
protocol data units of multiple MSs to an access relay station via
a tunnel link; the access relay station determines its own
reception of the tunnel data comprising protocol data units of
multiple MSs, and transmits feedback (reception acknowledgement
information or repeat request information) to the base station via
the tunnel link, or receives feedback from each MS about reception
of a corresponding protocol data unit which is sent via an access
link, then according to the feedback from each MS, applies for
bandwidth for retransmission or concentratedly transmits the
feedback from each MS to the base station via the tunnel link,
wherein, the access relay station extracts the protocol data unit
of each MS after successfully receiving the tunnel data comprising
the protocol data units of multiple MSs, and transmits the protocol
data unit of each MS to each MS via the access link. The tunnel
link is made up of multi-hop relay stations, the relay station
accessing the base station is the 1.sup.st hop relay station, and
the relay station accessing the MS is the n.sup.th hop relay
station, wherein, the 1.sup.st hop, the 2.sup.nd hop, . . . , the
(n-1).sup.th hop relay station will not transmit feedback
immediately to the base station after receiving the tunnel
data.
[0009] Wherein, the base station may allocate corresponding
channels for data transmission and feedback to each hop relay
station before transmitting the tunnel data. Each hop relay station
may know the feedback channel which is allocated to it by the base
station via its own calculation.
[0010] Wherein, when the t.sup.th hop relay station on the tunnel
link fails to receive the tunnel data comprising protocol data
units of multiple MSs, the t.sup.th hop relay station may transmit
repeat request information to the base station via the (t-1).sup.th
hop, the (t-2).sup.th hop, . . . , the 1.sup.st hop relay station
over the feedback channel which is allocated to it by the base
station.
[0011] If the tunnel end point (i.e., the access relay station)
receives the tunnel data comprising protocol data units of multiple
MSs successfully, the tunnel end point may feed back upwards
reception acknowledgement information immediately. If the access
relay station fails to receive the tunnel data comprising protocol
data units of multiple MSs, then the access relay station may feed
back upwards repeat request information immediately. The repeat
request information may be encoded to inform the base station that
in which hop a reception error of the tunnel data occurs.
[0012] If the t.sup.th relay station receives the tunnel data
comprising protocol data units of multiple MSs in the i.sup.th
frame correctly, the t.sup.th relay station may transfer feedback
from a downlink relay station to the base station in the
(i+m).sup.th frame, wherein, m=M*q+(M+1)*k, M is the number of hops
between the t.sup.th hop relay station and the tunnel end-point
relay station, q is the number of fixed delay frames of each hop
relay station for the tunnel data, k is a delay for hybrid
automatic repeat request feedback for the tunnel data on each hop
relay station. If the feedback received is reception
acknowledgement information, the t.sup.th hop relay station
transfers upwards without any change. If the feedback received is
repeat request information, the t.sup.th hop relay station may, by
encoding the repeat request information, inform the base station
that in which hop a reception error of the tunnel data occurs.
[0013] If the t.sup.th hop relay station fails to receive the
tunnel data comprising protocol data units of multiple MSs, the
t.sup.th hop relay station may feed back upwards repeat request
information over the feedback channel which is allocated to it by
the base station. The repeat request information may be encoded to
inform the base station that in which hop a reception error of the
tunnel data occurs.
[0014] If the tunnel data comprising protocol data units of
multiple MSs is a tunnel burst, the t.sup.th hop relay station that
has received the tunnel burst may determine whether it receives the
protocol data unit of each MS successfully according to a cyclic
redundancy check code which is carried by the protocol data unit of
each MS. The encoded repeat request information may include
information with respect to the t.sup.th hop relay station and
information with respect to connections of which protocol data
units are not received successfully by the t.sup.th hop relay
station.
[0015] If the tunnel data comprising protocol data units of
multiple MSs is a tunnel packet, the t.sup.th hop relay station
that has received the tunnel burst may determine whether it
receives the tunnel data comprising protocol data units of multiple
MSs successfully according to a cyclic redundancy check code of the
tunnel data comprising protocol data units of multiple MSs. The
encoded repeat request information may include information with
respect to the t.sup.th hop relay station and information with
respect to connections in the tunnel packet that are not received
successfully.
[0016] If the access relay station receives the tunnel data
comprising protocol data units of multiple MSs successfully, the
access relay station may transmit the protocol data unit of each MS
to each MS respectively.
[0017] Here, each MS may transmit the reception of the
corresponding protocol data unit to the access relay station, i.e.
suspending the hybrid automatic repeat request on the access link.
The access relay station may retransmit the corresponding protocol
data unit to the MS which fails to receive the corresponding
protocol data unit via pre-scheduled air interface resource. In the
event that the pre-scheduled air interface resource is insufficient
for retransmitting the corresponding protocol data unit to the MS
which fails to receive the corresponding protocol data unit, the
access relay station may apply again to the base station for the
air interface resource for retransmission.
[0018] Moreover, the access relay station may also report the
reception of the protocol data units at multiple MSs upwards to the
base station in a centralized report manner to complete the hybrid
automatic repeat request on the access link. Here, the access relay
station reports the reception of the protocol data units at
multiple MSs upwards to the base station via the feedback channel
which is pre-allocated by the base station. The access relay
station may retransmit the corresponding protocol data unit to the
MS which fails to receive the corresponding protocol data unit via
pre-scheduled air interface resource. In the event that the
pre-scheduled air interface resource is insufficient for
retransmitting the corresponding protocol data unit to the MS which
fails to receive the corresponding protocol data unit, the access
relay station applies again to the base station for the air
interface resource for retransmission.
[0019] According to the present invention, a hybrid automatic
repeat request method including the tunnel data transmission can be
perfected.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings illustrated here, which
constitutes a part of this application paper, are used to provide
further comprehension of the present invention, exemplary
embodiments of the present invention together with the descriptions
thereof serve to explain the present invention, but not constitute
inappropriate limitations to the present invention. In the
drawings:
[0021] FIG. 1 is a schematic diagram of a configuration of a
transparent wireless relay network according to embodiments of the
present invention;
[0022] FIG. 2 is a flow chart of a hybrid automatic repeat request
method of a downlink according to embodiments of the present
invention;
[0023] FIG. 3 is a schematic diagram of downlink tunnel data
retransmission according to embodiments of the present
invention;
[0024] FIG. 4 is a schematic diagram of an HARQ on a link-by-link
downlink tunnel adopting pre-scheduling on one access link
according to embodiments of the present invention;
[0025] FIG. 5 is a schematic diagram of an HARQ on a downlink
tunnel according to embodiments of the present invention;
[0026] FIG. 6 is a schematic diagram of an HARQ on a downlink
tunnel adopting pre-scheduling on one access link according to
embodiments of the present invention;
[0027] FIG. 7 is a schematic diagram of an HARQ on a downlink
tunnel according to embodiments of the present invention;
[0028] FIG. 8 is a schematic diagram of an example of centralized
feedback codes according to embodiments of the present
invention;
[0029] FIG. 9 illustrates a classification of a CID of tunnel data
according to embodiments of the present invention;
[0030] FIG. 10 is a schematic diagram of an example of tunnel
packet feedback encoding according to embodiments of the present
invention;
[0031] FIG. 11 is a schematic diagram defining an empty burst mode
according to embodiments of the present invention;
[0032] FIG. 12 is a schematic diagram defining an empty burst
format according to embodiments of the present invention;
[0033] FIG. 13 is a schematic diagram defining a feedback delay
notice mode according to embodiments of the present invention;
and
[0034] FIG. 14 is a schematic diagram of a feedback delay notice
format according to embodiments of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The embodiments of the present invention will be described
below in detail with reference to the drawings.
[0036] Referring to FIG. 1, a configuration of a transparent
wireless relay network according to embodiments of the present
invention is illustrated. As shown in FIG. 1, RS3 accesses multiple
MSs, accordingly, one relay tunnel may be set up between the RS3
and a MR-BS. Protocol Data Units (PDU) of multiple MSs may make up
one tunnel burst by the MR-BS to act as a basic unit of an HARQ to
be transmitted in one frame. After the tunnel burst reaches the RS3
successfully, the RS3 restores the PDU of each MS, and continues to
accomplish the HARQ accomplished on an access link.
[0037] Referring to FIG. 2, a hybrid automatic repeat request
method of a downlink according to embodiments of the present
invention is illustrated. The method includes the following steps:
S202, a base station transmits tunnel data comprising protocol data
units of multiple MSs to an access relay station via a tunnel link,
and receives feedback from a relay station until the access relay
station receives data correctly; S204, the access relay station
extracts the protocol data unit of each MS from the tunnel data,
transmits the protocol data unit of each MS to the corresponding
MS, and performs corresponding processing after receiving feedback
from each MS. Wherein, the tunnel link is made up of multi-hop
relay stations, the relay station accessing the base station is the
1.sup.st hop relay station, and the relay station accessing the MS
is the n.sup.th hop relay station, wherein, the 1.sup.st hop, the
2.sup.nd hop, . . . , the (n-1).sup.th hop relay station will not
transmit reception acknowledgement information to the base station
immediately after receiving the tunnel data. Wherein, the
corresponding processing is, after the access relay station
receives the feedback from each MS, uplink relaying the feedback
from the MSs to the base station or not uplink relaying the
feedback but applying for bandwidth for retransmission according to
the feedback from the MSs.
[0038] The processing of the above steps will be described
hereinafter in detail.
[0039] In Step S202, as shown in FIG. 3, the RS is not required to
provide feedback immediately after receiving the tunnel data, but
continues to transfer the data. The MR-BS has allocated a
corresponding feedback channel for each RS to transfer the feedback
(tunnel data ACK/NAK) before the RS transmits certain tunnel data.
Each RS may know the feedback channel allocated to itself by its
own calculation, and transmits the feedback over corresponding
resource. Here, the feedback from the RS3 is not received from the
MS, but is generated locally from itself. There is no need to
consider the access link in the calculation of the feedback time of
all RSs.
[0040] The regulation for calculating a feedback delay for an
end-to-end tunnel burst HARQ is provided by the following formula:
m=M*q+(M+1)*k. Wherein, M is the number of hops between the RS and
the tunnel end point; q is the number of fixed delay frames of the
RS for the tunnel burst; k is the delay for the HARQ feedback for
the tunnel burst defined by the system, which may be provided in
system broadcast information depending on the situation.
[0041] Wherein, the specific implementation may use, but is not
limited to the following method: adding the number of hops between
each station and the tunnel end point to the field of the number of
hops (hop depth) of the sub-burst information element (IE) of the
tunnel data. Each station on the tunnel calculates the time for
transferring the tunnel feedback by applying the value M to the
above formula.
[0042] Moreover, if the RS does not transfer the tunnel burst
successfully, it is necessary to feed back the failure over the
pre-arranged feedback channel. The MR-BS restarts to schedule the
next transfer. This step will end if and only if the tunnel data
reaches the access RS successfully. Accordingly, it is necessary to
define encoded feedback to denote different situations of the
tunnel data transmission.
[0043] As shown in FIG. 4, when the tunnel data fails to be
transmitted on the link, the encoded tunnel data NAK should be fed
back to the MR-BS according to the pre-scheduling of the MR-BS.
According to the codes, the MR-BS determines the RS that has
failing transmission, and schedules corresponding resource to
retransmit the failed tunnel data.
[0044] When the tunnel data is a tunnel packet, a CRC check code is
added to the packet itself. The RS may determine whether the
reception is successful according to the CRC check code of the
packet. If the tunnel packet fails to be received, the entire
tunnel packet may be retransmitted. The MR-BS is required to
allocate only half a sub-channel for the tunnel packet feedback as
a feedback channel, it is equivalent to take one tunnel packet as
one ordinary sub-burst, the feedback channel is saved greatly, but
the cost is that data channels for retransmission always occupy the
tunnel packet size. The feedback on the NAK of the tunnel packet is
only required to reflect that in which hop the failure occurs, and
the corresponding codes may be shown as FIG. 8. The feedback code
D0 indicates that the tunnel packet is transmitted successfully.
Each relay transmits D0 to the MR-BS without any change after
receiving D0. If the tunnel data fails to be transmitted in the
x.sup.th hop, the start point of this hop, RSx, will transmit D1,
RS(x-1) receiving D1 will add one to the code, and then transmits
D2. Through cycling like this, the MR-BS may know that it is
necessary to re-arrange resource to transmit the tunnel packet in
the x.sup.th hop when receiving the feedback encoded as a Dx.
[0045] Furthermore, the MR-BS may also arrange a corresponding
feedback channel for each connection in the tunnel packet. Here,
the advantage of the tunnel packet is that if the tunnel burst is
transmitted successfully, it may be checked out at one time that
all PDUs are transmitted successfully by using the CRC carried by
the packet itself, and then all the connections are required to
feed back codes which represent success over their own feedback
channels. Correspondingly, if the tunnel burst fails to be
transmitted, the RS shall check out the connection that has an
error transmission according to the CRC check code carried by each
PDU itself, and then transmits feedback using codes in the existing
16j standard. After receiving the feedback code in the existing
standard, the MR-BS will arrange retransmission of the tunnel
packet according to the feedback. The retransmitted packet will
only carry the PDU of the connection that had an error transmission
last time. In this way, the feedback channel will be enlarged, but
the overhead of the data transmission channel will be reduced.
[0046] When the tunnel data is a tunnel burst, the burst itself
does not carry the CRC check code. The RS should determine
respectively whether the PDU is received successfully according to
the CRC check code carried by each PDU itself which constitutes the
tunnel burst, and finally, determines whether the entire burst is
received successfully. If the failure of receiving a part of PDUs
leads to the failure of receiving the tunnel burst, it is only
required to retransmit the corresponding PDU, therefore, the
feedback code of the tunnel burst is required not only to reflect
the hops in which the failure occurs, but also to reflect the PDU
of the connection in which the failure occurs. Therefore, the
feedback channel of the tunnel burst is actually the collection of
feedback channels of all connections on the tunnel. Each sub-burst
making up the burst may feed back its reception using the codes
shown in FIG. 8. The RS collects the feedback from each sub-burst
of the tunnel burst, and concentratedly transmits the feedback over
the feedback channel which is allocated by the base station. The
MR-BS will arrange retransmission of the tunnel burst according to
the feedback after receiving the existing centralized feedback
codes. The retransmitted burst will only carry the sub-burst
corresponding to the PDU of the connection which had an error
transmission last time.
[0047] Moreover, in the existing IEEE802.16j standard technology,
each MS (distinguished by a RCID) can only carry 16 connections at
most and accordingly has 16 sub-channels, therefore 4 bits may be
used to constitute a feedback subchannel identifier (ACID).
However, in the tunnel burst, RCIDs of different sub-bursts are
replaced by the same TCID, the ACID of each MS may conflict at this
moment, and moreover it can not be identified that which sub-burst
has an error. Therefore, as shown in FIG. 9, the tunnel packet TCID
and the tunnel burst TCID of bursts may be defined in section in
the TCID definition. In this way, the tunnel packet mode and the
tunnel burst mode can be distinguished by the TCID in transmission.
In the tunnel packet mode, the ACID of the corresponding sub-burst
is still 4 bits. In the tunnel burst mode, the ACID of the
corresponding sub-burst is defined as 8 bits and is sorted again,
in this way the conflict of the ACIDs can be avoided.
[0048] In Step S204, the access RS (the start point of the access
link) has stored the burst on each access link, and the MR-BS
should arrange the channels for burst retransmission and feedback
on the access link.
[0049] The characteristic of the embodiment 1 is a link-by-link
HARQ, the so-called link-by-link, as shown in FIG. 1, means that
the tunnel HARQ is one link and each access link between the access
RS at the tunnel end point and each MS is another link. The data is
transmitted over transmission links which are made up of two links
respectively in different combination formats. The transmission
over the two links respectively adopts an end-to-end HARQ. In this
way, new data may begin to be transmitted as long as the tunnel end
point receives the tunnel data successfully. Compared to the case
where the MR-BS can transmit new data only if it receives feedback
from the MS, the efficiency of data transmission is obviously
improved in the embodiment of the present invention.
[0050] In the embodiment 1, the feedback on the access link is only
required to be transmitted to the access RS. However, if the burst
transmission fails on the access link, the access RS must apply for
bandwidth retransmission and give feedback to the MR-BS. In order
to improve the retransmission efficiency of the access link, it may
be considered to adopt pre-scheduling on the access link.
[0051] As shown in FIG. 4, the MR-BS may pre-schedule appropriate
air interface resource for retransmission on the access link
according to link information of the access link. In case the MS
reports to the uplink RS3 that a burst fails to be received on the
access link, the RS3 may begin to retransmit the failed burst
immediately on the pre-scheduled air interface resource, without
waiting the MR-BS to arrange new air interface resource. The
pre-scheduled resource (i.e., pre-scheduling the number of times of
retransmission as well as sub-channels for retransmission) may be
adjusted according to channel information reported upwards by the
access link.
[0052] If all bursts on the access link are transmitted
successfully before the pre-scheduling resource is exhausted, the
access RS need not feed back again. If some bursts of the MS are
still not transmitted successfully after the pre-scheduling
resource is exhausted, the access RS must apply resource to the
MR-BS for retransmitting the failed bursts. This application may
use an HARQ error report message defined by the IEEE802.16j
standard in the existing technology.
[0053] The characteristic of the embodiment 2 is link-by-link
transmission, and that feedback about the MS burst may be
transmitted to the MR-BS. As shown in FIG. 5, the MS burst may
begin to be transmitted only after the tunnel link data is
transmitted successfully. ACKs/NAKs of all MSs are collected by the
access RS, and then are fed back to the uplink RS concentratedly,
and finally are transferred to the MR-BS. The MR-BS schedules the
resource and arranges to retransmit the failed MS burst according
to the received feedback.
[0054] The characteristic of the embodiment 3 is that feedback
about the MS burst may be transmitted to the MR-BS and that the
MR-BS may pre-arrange a transmission link from the MR-BS to the MS
(as shown in FIG. 7). If the tunnel data is transmitted to the RS3
without retransmission and are received by the RS3 successfully,
the MS burst in the tunnel data may be taken out by the RS3
immediately and be transmitted to the MS. But the cost is that
pre-arranged resource will be wasted in case the tunnel data is not
transmitted successfully.
[0055] For the embodiment 2 and embodiment 3, as shown in FIG. 6,
in order to improve the retransmission efficiency, the MR-BS may
pre-schedule appropriate air interface resource for retransmission
on the access link according to the link information of the access
link. In case the MS reports that the burst fails to be received on
the access link, the retransmission may begin immediately on the
pre-scheduled air interface resource without waiting the MR-BS to
arrange new air interface resource. After the pre-scheduled
resource is exhausted, the access RS must, after collecting every
result of retransmission based on the pre-scheduled resource on the
access link, report them upwards to the MR-BS no matter whether the
retransmission is successful.
[0056] For the embodiment 2 and embodiment 3, the manner of
reporting the centralized feedback may use, but is not limited to
the following manners. The MR-BS may arrange one dedicated
HARQ_ACKCH area for the access RS to report the centralized
feedback. The sequence of the feedback in the area may be
designated by the MR-BS according to the sequence of the
connections or bursts, or may also adopt an encoding manner. An
encoding manner of the centralized feedback is shown in FIG. 10,
the feedback of three bursts in this figure may be encoded in one
group, and is denoted by three tiles defined in the IEEE 802.16j
standard. The combinations of different codes are orthogonal to
each other, and denote different situations of MS burst
transmission. For example, the feedback code A0 denotes that three
bursts are all received correctly, and the feedback code A1 denotes
that an error transmission of the first burst in low bits occurs on
the access link while the other two bursts are received
correctly.
[0057] For the embodiment 2 and embodiment 3, it is required to
trigger the RS to transfer the centralized feedback when the
centralized feedback is reported. But in the existing technology,
the RS may be triggered only when it receives the data that is to
be transferred. It is not defined in the existing technology
regarding to how to trigger the RS to transfer the feedback when
the burst is retransmitted on the access link but the RS fails to
receive the data. In order to resolve the problem, specific methods
may include, but is not limited to, the two methods as below.
[0058] Method One is using empty data to trigger. An empty burst,
HARQ burst, is defined in FIG. 11, and the burst format of the
empty burst, HARQ burst, is defined in FIG. 12.
[0059] The so-called empty data refer to the data without any data
transmission. For the embodiment 2 and embodiment 3, there are
several empty bursts in one empty data. The centralized feedback is
the collection of the corresponding empty bursts. The RS which
receives the empty data only calculates the delay for the feedback
about transferring the empty data. A formula for calculating the
delay is given as follows:
[0060] if the RS receives the empty data in the i.sup.th frame, the
feedback should be given in the (i+n).sup.th frame, wherein, n is
determined by the formula (1).
n=H*p+(H+1)*j+s (2)
[0061] in the formula (2), H is the number of the hops between the
RS and the end point of the link, p is the number of fixed delay
frames of the RS, j is a feedback delay for the HARQ defined by the
system and is provided in a system broadcast message; s is a delay
for the access RS collecting feedback from all RSs.
[0062] Method Two is notifying the RS directly of the delay
required for transferring the feedback. The notice mode of the
feedback delay is defined in FIG. 13. The notice format of the
feedback delay is defined in FIG. 14. The RS which receives the
notice will wait for the corresponding time according to the delay
information in the notice and then transfers the feedback from the
designated connection directly.
[0063] The above descriptions are just embodiments of the present
invention and are not used to limit the present invention, for
those skilled in the art, various modifications and variations can
be made to the present invention. Any modification, equivalent
substitution or improvement, etc. within the spirit and principle
of the present invention shall be included in the scope of claims
of the present invention.
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